Project Summary/Abstract: Research efforts will focus on fabrication of ultraviolet (UV) light emitting diodes (LEDs) in the emission range of 305 nm to 315 nm for phototherapy of psoriasis. Successful production of UV sources in this wavelength range will enable research for new phototherapy treatment programs for psoriasis and possibly other skin diseases including acne vularis, atopic dermatitis, vitiligo, pruritus, lichen planus, pityriasis rosea and early cutaneous T-cell lymphoma. To design and implement effective light treatments, UV sources at specific wavelengths and power densities have to be available within the action spectrum for clearing psoriasis. Wavelengths shorter than 295 nm produce phototoxicity at higher doses with no positive effect on the psoriasis. At wavelengths above 315 nm, reactions with the skin tissue is greatly reduced, with exposure in the UVA region requiring about 1000 times the dose compared to UVB with very limited success observed on small exposure sites. This suggests that monochromatic radiation at specific wavelengths may be more therapeutic than exposure to broadband sources. All phototherapy in the UV range is limited by injurious exposure to radiation on normal uninvolved skin adjacent to the affected areas and strict control of wavelength, doses, distribution and delivery are required. UV light sources are a core enabling technology in phototherapy for treatment of specific skin diseases such as psoriasis. Today, these light sources are primarily broadband high pressure mercury lamps, mercury xenon, mercury argon and deuterium sources or excimer lasers. In practice, this has meant that phototherapy treatment methods have had to be adapted to the available light source wavelengths rather than optimizing the light sources to specific wavelength(s) of interest. This proposal concentrates on the development of LEDs based on aluminum gallium nitride (AlGaN) alloys that can cover a large and useful portion of the UV spectrum. These semiconductor devices are compact (about the size of a grain of rice), stable over long lifetimes, and require simple drive electronics. Each device has a narrow emission spectrum that is tuned by adjusting the composition and structure of the active layers of the device during manufacture. Thus, a combination of the UV LEDs can deliver a specific, selectable spectrum (via electronic control) over the wavelength range they cover. Broadband UVB, narrow band UVB, broadband UVA, photochemotherapy (PUVA) and photodynamic therapy (PDT) are among the applications in which UV sources are required. Project Narrative: Nitride based UV LEDs emitting in the 305 nm to 315 nm (UVB) range can be successfully employed in phototherapy of certain illnesses and skin diseases. This wavelength range has proven effective in treating psoriasis. Existing psoriasis phototherapy treatments are costly and time consuming and can interfere with employment or school schedules. A need exists in which an inexpensive compact UV apparatus based on 305 nm to 315 nm LEDs can be prescribed to a patient for in-home use for the treatment of psoriasis. [unreadable] [unreadable] [unreadable]